# MOSFET problem

Discussion in 'Homework Help' started by tadm123, Dec 3, 2013.

Nov 20, 2013
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The parameters of MOSFET:

Vt=1V
kn'=μCi=0.1[mA/V]
λ=0.02
L=4u
W=20u

Here's the formula for saturation

I don't know where to start and I been thinking what to do for almost 1:30 hours. I tried plugging in the values into the formula and then solving for VG to get the RG values, but that doesnt' work either. What can I do to start solving this problem?
Any help would be appreciated.

Last edited: Dec 3, 2013

Nov 20, 2013
43
0
I guess my question is what's the relationship between RG and ID

3. ### shteii01 AAC Fanatic!

Feb 19, 2010
4,436
703
From my textbook, section MOSFET Small-Signal Amplifier

"RG establishes the Q-point on the load line.

If we assume that v_in=V_in*sin(wt), the gate-to-source voltage will have a sinusoidal signal superimposed on the dc quiescent value. As the gate-to-source voltage changes over time, the Q-point will move up and down the line.
Moving up and down the load line translates into a sinusoidal variation in the drain current."

So. RG sets up the Q-point. Then everything else oscillates around that point.

Last edited: Dec 3, 2013
4. ### WBahn Moderator

Mar 31, 2012
23,166
6,976
(Q1) What's the relationship between Vg and Id?

(Q2) What's the relationship between Rg and Vg?

tadm123 and anhnha like this.
5. ### Jony130 AAC Fanatic!

Feb 17, 2009
4,510
1,272
In saturation we use this equation to find Id current

$\Large I_{D} = \frac{1}{2}\mu_n C_{ox} \frac{W}{L} (V_{GS} - V_{TH})^2(1 + \lambda V_{DS})$